Connecting powered sub to AVR with no sub out
I'm going to buy a cheap sub (Dayton Sub1000) and connect it with my old AVR. This AVR is 5.1 but has not output for powered sub, it uses regular speaker wires to connect to a passive sub. There is also no crossover setting. I've tested it with a passive sub connected, the sub plays sound up to around 200 Hz. Either the AVR sends full spectrum to all channels or it has an internal crossover that can't be changed.
Given the Dayton has speaker level inputs, should I hook it up to the front L/R and connect the speakers to the sub, or is it better to leave the speakers alone and hook it up to the passive sub output (run wire from passive sub out to speaker level inputs on the sub)?